acrylic bouncing during cuts

[Jonathan Bowen]

So I'm trying to figure out why my machine is shifting the pieces as I cut. It happens with MDF and acrylic. I hear a bang from the machine and the piece moves. It has screwed up some cuts and bounced so hard that smaller pieces have bounced up onto the sheet and got in the way of another cut. I'm only seeing it when I cut for long times on a full sheet (16" by 12" about 20-60 min cutting times)

I have noticed flame bursts when cutting mdf. Not sure if they are connected. The z-motor doesn't move. I'm using a honeycomb table. Can the gasses be building up and exploding? I'd blame it on the air compress doing stupid stuff but that seems to be running fine. I've left the blower, compressor, and chiller on for a long time without the laser running and I have not heard the banging.

Any ideas?

[Scott Shepherd]

We had insufficient air flow for a short time and I've seen that happen a lot, especially with acrylic. The gas builds up in the honeycomb flutes and then "pops". I cut clear acrylic in a test and you can see the mini-explosion happen. Since correcting that airflow issue, I've never seen or heard it again. But it's basically not enough air being pulled through the system to get the vapors out of the honeycomb.

[Mark Sipes]

What machine do you have???? table size, power, make. Banging as in mechanical metal to metal. Does the machine jump around also like an unbalanced washing machine as the head travels? gases burning should not make a banging sound as they burn unless there is a vey large pocket, which if the exhaust is working will not occur.

[greg lindsey]

I absoluelty agree with Scott, I had the same problem, I had forgot to turn the blower on. The acrylic jumped off the table with a loud boom, scared the hell outta me as I was watching it when it happened. Turned the blower on ( then changed my shorts :eek:) and all was good. Good airflow is a must.

[Chuck Stone]

I had something similar happen with acrylic, but it stopped when I fixed the 'honeycomb'.
I don't have one, so I use the white plastic grids for fluorescent lighting. I cut it to size
and use that instead of a honeycomb table. If I just use it raw, the air doesn't move. So
the first thing I do is cut channels across, then front to back.Don't cut all the way through,
obviously.. but it lets the air get pulled out from the grid. No more pops.
It keeps the acrylic a lot cleaner, too. (and the grid)

[Jonathan Bowen]

It's a 40 watt Hurricane Lasers Agnes. I'm cutting a large file for a customer right now. I took some video to send to the manufacturer. It is popping. I caught the flames on video. Blower is on. Air is on. Do I need to elevate the honeycomb with some rubber feet to help with the air flow?

[Chuck Stone]

It's a 40 watt Hurricane Lasers Agnes. I'm cutting a large file for a customer right now. I took some video to send to the manufacturer. It is popping. I caught the flames on video. Blower is on. Air is on. Do I need to elevate the honeycomb with some rubber feet to help with the air flow?

A couple of quarters at each end should do it

[Scott Shepherd]

It's a 40 watt Hurricane Lasers Agnes. I'm cutting a large file for a customer right now. I took some video to send to the manufacturer. It is popping. I caught the flames on video. Blower is on. Air is on. Do I need to elevate the honeycomb with some rubber feet to help with the air flow?

Is has nothing to do with the air being on, it's what I said, not ENOUGH air flowing to get the fumes out of the cabinet. Try what Chuck said and elevate it. Maybe your airflow is fine, but it's just trapped under the table. If raising it doesn't help, you need to move more CFM through the cabinet. I had a 950 CFM blower shared between 2 machines when I had the issue. Now each laser has it's own blower, both at 950 CFM and i've never seen the problem since.

[Joe Pelonio]

I agree, you need more power. You should be able to drop a sheet of paper near the air intake and see it immediately sucked up flat against the machine. Also, do make sure your honeycomb is not sitting on the flat solid bottom. On my Epilog the honeycomb is mounted on a frame that allows air in all around the side, then through the honeycomb and cuts.